The present invention relates to a driving system for driving a plasma display panel (PDP) of a matrix display type.
Recently, as a display device becomes large in size, thickness of the display device is desired to be thin. Therefore, various types of display devices of thin thickness are provided. As one of the display devices, an ACPDP is known.
A conventional ACPDP comprises a plurality of data electrodes, and a plurality of row electrodes formed in pairs and disposed to intersect the data electrodes. A pair of row electrodes form one row (one scanning line) of an image. The data electrodes and the row electrodes are covered by dielectric layers respectively, at a discharge space. At the intersection of each of the data electrodes and each pair of row electrodes, a discharge cell (pixel) is formed.
As a method for displaying an image on the PDP, each frame (field) of a video signal is divided into N pieces of sub-frames (sub-fields), and each sub-frame (sub-field) emits the light for a time length corresponding to a weight applied to each bit of n-bit pixel data (sub-frame method).
In the method, if a pixel data for each pixel has 6 bits, each frame is divided into six sub-frames, SF1, SF2, . . . SF6. The sub-frames SF1 to SF6 emit the light by sustaining discharge at 1 time, 2 times, 4 times, 8 times, 16 times and 32 times, respectively, in order. Thus, the tone of 64 steps can be obtained by combining the six sub-frames.
However, in such a method, when an image is moved in plane on the PDP, false contours of stripes are recognized as if the tone of the image is lost near the area where the image crosses the border at the tone level of the n power of 2 such as 32nd or 16th. Therefore, a problem that the quality of display is extremely deteriorated arises. In order to reduce the false contours, thereby restraining reduction of the quality of display, the method wherein a sub-frame having a large weight is divided into a plurality of parts, and these parts are separately disposed in a frame has been proposed.
There are two cases in the PDP that, a video signal (interlace video signal) produced by the interlace scanning as used in the NTSC system is displayed, and that a video signal (non-interlace video signal) produced by the non-interlace scanning as used in the personal computer is displayed.
In the display using the interlace video signal, light emitting luminance is low. Therefore, the interlace video signal is processed by the scanning line interpolation to be converted into the non-interlace video signal, thereby obtaining the same amount of data as the non-interlace video signal. However, if the false contour process is carried out on the converted non-interlace video signal, the number of sub-frames in one frame (field) period increases. On the other hand, since the computer picture image is mainly still picture, it is not necessary to process the false contour. However, in the display of the NTSC system, the interlace video signal is used for mostly displaying a moving picture. In order to improve the quality of the display of the interlace video signal, it is necessary to process false contour correction.
Furthermore, in order to improve the picture quality of the display of NTSC system using the interlace video signal, if the number of bits of a pixel data is increased, the number of sub-frames in one frame (field) is further increased. As a result, it is necessary to increase a capacity of a memory for the false contour correcting process and the improvement in the picture quality. Therefore, a problem that manufacturing cost is increased arises.